Abstract: In order to eliminate sidewall fusion defects commonly associated with laser ultra-narrow gap welding, a dot-ring laser filling welding process was developed.The welding wire was heated using a central spot laser, while the narrow gap bevel was heated using a ring laser. Welding was successfully performed on a 30 mm thick 10CrNi3MoV high strength steel, and a comparative analysis of the microstructure and properties with a traditional arc-welded joint was conducted. The results indicate that the weld zone of the laser ultra-narrow gap filling welded joint consists of acicular ferrite, granular bainite and a small amount of martensite, while the arc-welded joint is composed of acicular ferrite and granular bainite. The rapid cooling characteristic of laser welding results in a finer microstructure compared to arc welding.The heat-affected zone of the laser-welded joint is characterized by a higher proportion of ferrite and granular bainite, and a lower proportion of M-A constituents, contributing to improved joint performance.The tensile strength of the laser ultra-narrow gap filling welded joint is approximately equivalent to that of the arc-welded joint, but the former exhibits superior impact toughness.